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HIGH FREQUENCY ULTRASONIC PHASED ARRAY SYSTEM AND ITS
APPLICATIONS
by
Fan Zheng
A Dissertation Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(BIOMEDICAL ENGINEERING)
December 2012
Copyright 2012 Fan Zheng

While similar to a linear-switched array in structure, an ultrasound linear phased array (simply called phased array) is quite different in operation. It is capable of beam steering to form fan-shaped sector images without inducing grating lobes. Moreover, the relative smaller array footprint is useful where only very limited contact surface is permitted. High frequency phased arrays combine the advantages of the phased array and high frequency ultrasound, which offer both small footprint and high spatial resolution. This dissertation reports the design and development of a digital ultrasonic imaging platform with raw RF data acquisition capability, which can be paired with a prototype 64-element 26 MHz phased array transducer. A wire phantom image showed that -6 dB lateral and axial resolutions were 209 and 104 μm, respectively, which were in good agreement with the Field II simulation. Anechoic cyst tissue-mimicking phantom images demonstrated its capability to detect cysts of 300 μm in diameter. An image of a rabbit eyeball in vitro was also acquired. This imaging platform is designed for the purpose of testing high frequency phased arrays under development as well as facilitating the development in novel array signal processing algorithms. ❧ Without additional change in the system hardware, the current high frequency array system can be also applied in the industrial non-destructive testing (NDT) applications. A motorized XY stage allows the array system to acquire C-mode scan as well as normal B-mode scan with bigger scanning area. Electronic scanning in array system could dramatically reduce the total scanning time compare to single element system. An aluminum sample and a silicon carbide sample were examined to test the system in non-destructive testing. ❧ Besides the applications in biomedical imaging and non-destructive testing, the high frequency ultrasonic phased array and system are shown to be capable of trapping and translating microparticles precisely and efficiently, made possible due to the fact that the acoustic beam produced by a phased array can be both focused and steered. Acoustic manipulation of microparticles by a phased array is advantageous over a single element transducer since there is no mechanical movement required for the array. Experimental results show that 45 μm diameter polystyrene microspheres can be easily and accurately trapped and moved to desired positions by a 64-element 26 MHz phased array.

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HIGH FREQUENCY ULTRASONIC PHASED ARRAY SYSTEM AND ITS
APPLICATIONS
by
Fan Zheng
A Dissertation Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(BIOMEDICAL ENGINEERING)
December 2012
Copyright 2012 Fan Zheng